And as they went on [their] way, they came unto a certain water: and the eunuch said, See, [here is] water; what doth hinder me to be baptized?

Note 7 at Ac 8:36: Judging from the eunuch's lack of understanding of the scriptures in Isa 53, it is not probable that he knew about water baptism from Scripture. It can therefore be assumed that Philip included instruction about water baptism in his preaching of Jesus (Ac 8:35). However, as explained in note 9 at Mr 16:16 and note 2 at Ac 2:38, water baptism is only a sign of salvation and not something we do in order to obtain salvation.